- Define a _spinunlock() function so that threading implementations may do

more complicated things than just setting the lock to 0.
 - Implement stubs for this function in libc and the two threading libraries
   that are currently in the tree.

lib/libc/gen/_spinlock_stub.c

@@ -43,6 +43,7 @@ __FBSDID("$FreeBSD$");
  */
 __weak_reference(_atomic_lock_stub, _atomic_lock);
 __weak_reference(_spinlock_stub, _spinlock);
+__weak_reference(_spinlock_stub, _spinunlock);
 __weak_reference(_spinlock_debug_stub, _spinlock_debug);
 
 
@@ -64,6 +65,14 @@ _spinlock_stub(spinlock_t *lck)
 {
 }
 
+/*
+ * This function is a stub for the spinunlock function in libpthread.
+ */
+void
+_spinunlock_stub(spinlock_t *lck)
+{
+}
+
 /*
  * This function is a stub for the debug spinlock function in libpthread.
  */

lib/libc/include/spinlock.h

@@ -52,7 +52,7 @@ typedef struct {
 
 #define	_SPINLOCK_INITIALIZER	{ 0, 0, 0, 0 }
 
-#define _SPINUNLOCK(_lck)	(_lck)->access_lock = 0
+#define _SPINUNLOCK(_lck)	_spinunlock(_lck);
 #ifdef	_LOCK_DEBUG
 #define	_SPINLOCK(_lck)		_spinlock_debug(_lck, __FILE__, __LINE__)
 #else
@@ -65,6 +65,7 @@ typedef struct {
 __BEGIN_DECLS
 long	_atomic_lock(volatile long *);
 void	_spinlock(spinlock_t *);
+void	_spinunlock(spinlock_t *);
 void	_spinlock_debug(spinlock_t *, char *, int);
 __END_DECLS
 

lib/libc_r/uthread/uthread_spinlock.c

@@ -44,6 +44,12 @@
 
 #include "pthread_private.h"
 
+void
+_spinunlock(spinlock_t *lck)
+{
+	lck->access_lock = 0;
+}
+
 /*
  * Lock a location for the running thread. Yield to allow other
  * threads to run if this thread is blocked because the lock is

lib/libkse/thread/thr_spinlock.c

@@ -44,6 +44,13 @@
 
 #include "thr_private.h"
 
+void
+_spinunlock(spinlock_t *lck)
+{
+	lck->access_lock = 0;
+}
+
+
 /*
  * Lock a location for the running thread. Yield to allow other
  * threads to run if this thread is blocked because the lock is

lib/libpthread/thread/thr_spinlock.c

@@ -44,6 +44,13 @@
 
 #include "thr_private.h"
 
+void
+_spinunlock(spinlock_t *lck)
+{
+	lck->access_lock = 0;
+}
+
+
 /*
  * Lock a location for the running thread. Yield to allow other
  * threads to run if this thread is blocked because the lock is